Alexander Polyakov | Sevastopol State University (original) (raw)

Papers by Alexander Polyakov

Research paper thumbnail of New Laguerre-S Type Method For Solving Of A Polynomial Equations Systems

In this paper we present a substantiation of a new Laguerre-s type iterative method for solving o... more In this paper we present a substantiation of a new Laguerre-s type iterative method for solving of a nonlinear polynomial equations systems with real coefficients. The problems of its implementation, including relating to the structural choice of initial approximations, were considered. Test examples demonstrate the effectiveness of the method at the solving of many practical problems solving.

Research paper thumbnail of Multicriteria Synthesis Of A Polycentric Knee Prosthesis For Transfemoral Amputees

In one of the prosthesis designs for lower limb transfemoral amputations artificial knee joints w... more In one of the prosthesis designs for lower limb transfemoral amputations artificial knee joints with polycentric mechanisms are used. Such prostheses are characterized by high stability during the stance phase of the movement. The existing variety of polycentric mechanisms indicates the possibility of finding the optimal prosthesis design satisfying several quality criteria.In this paper we present a multicriteria method for the synthesis of the artifical polycentric knee mechanism based on the uniform systematic study of the design parameters space and on the analysis of Pareto optimal solutions.

Research paper thumbnail of Manipulator synthesis on the given properties of working space. Application of polynomials with linear real parameter

2010 IEEE International Conference on Systems, Man and Cybernetics, 2010

Abstract-In this work the algorithm and the results of a synthesis problem solving for three-link... more Abstract-In this work the algorithm and the results of a synthesis problem solving for three-links planar manipulator with anthropomorphous structure according to criterion of a minimum total volume of links movements is resulted at achievement by end effector of set of points in ...

Research paper thumbnail of System Analysis and Synthesis of Total Hip Joint Endoprosthesis

Procedia Engineering, 2015

Research paper thumbnail of A Novel Fatigue Testing Machine For Spinal Fixation Systems Under Various Conditions Of Loading

SAÜ Fen Bilimleri Enstitüsü Dergisi, 2012

For recent years, a new technologies of treatment of spinal disease and injuries received underwe... more For recent years, a new technologies of treatment of spinal disease and injuries received underwent rapid development. Many of them use different types of artificial implants and fixation systems. At the same time the most widely a transpedicular and ventral systems are used. If the spinal surgical operation is performed by the modern technology, patients quickly acquire the ability to lead an active life, during which the elements of the fixation systems (screws, longitudinal and transverse rods) are subjected to intensive loading and for various reasons may lose its functionality. One such reason is the fatigue of design elements. Efficiency of fixation system components is determined by the quality of their surgical implantation, taking into account the mechanical characteristics of materials and the design features. It is rather difficult to take into consideration the influence of all factors and to quantify the resource of the known and newly designed structures. The most accurate estimates can be obtained through the testing only. In this work is presented a new design of the machine for fatigue tests of spinal fixation systems, which allow to obtain reliable estimates of the resource under different loading conditions.

Research paper thumbnail of Improving the Finite Element Simulation of Wear of Total Hip Prosthesis’ Spherical Joint with the Polymeric Component

Procedia Engineering, 2015

Research paper thumbnail of Evaluating the Impact and Norming the Parameters of Partially Regular Texture on the Surface of the Articulating Ball Head in a Total Hip Joint Prosthesis

Tribology Online, 2016

The theoretical study and evaluation of stress-strain condition of the friction pair's surfaces o... more The theoretical study and evaluation of stress-strain condition of the friction pair's surfaces of total hip joint prosthesis with partially regular texture on a ball head surface, depending on the values of its characteristic parameters, using finite element modeling are performed. It has allowed formulating the recommendations for dimple's spacing rationing and the extent of a surface rough site with partially regular texture, aiming to increase the prosthesis' lifespan. The problem is solved from the condition of dry or boundary lubrication. For the indicated range of nominal contact pressure in hip joint, the quantitative evaluation of allowable roughness parameters to which it is necessary to process the ball head surface for metal-on-metal and metal-on-polymer friction pairs are obtained, considering the dimple's spacing and size on the surface.

Research paper thumbnail of Modeling stress–strain state of screw transpedicular spine fixation system with variable structure of the vertebral body

Journal of Biomechanics, 2011

Research paper thumbnail of Structure and kinematics of the stand for testing implants with actuator on the basis artificial pneumatic muscle

Journal of Biomechanics, 2011

ABSTRACT Parallel manipulators, based on platform Stewart-type, have a number of advantages, whic... more ABSTRACT Parallel manipulators, based on platform Stewart-type, have a number of advantages, which are essential in the implementation of the required spatial motions of a rigid mobile platform and any fixed relative to its parts or devices. Such a problem arises, for example, if necessary, testing of implants, which replace the elements of the spine and stabilization systems of local areas of the spine, for example, transpedicular or ventral systems. During the tests necessary to most accurately reproduce the natural movement of one of the elements tested systems, and for some implants standards strictly define the test conditions. Preliminary calculations made by us have shown that the angular and linear movement of the mobile test bed, based on platform type manipulator is used by Stewart, are relatively small. In this regard, suggested as a pneumatic actuator using artificial muscles, produced by FESTO. Thus, the structure appears to stand rigid fixed platform, which is associated with the mobile platform with six artificial muscles, each of which is attached to both platforms by means of spherical joints. In a medium Solidworks we have developed three-dimensional models of stands of various types in order to assess their functional capabilities and selection of optimal, in terms of kinematics, dynamics and control. Kinematics of the Stewart platform is sufficient detail considered in many sources. Therefore the most important the task is developing an interconnected qualitative algorithm for solving direct and inverse kinematics. In future this algorithm will be used in the synthesis of system control actuators platform (artificial muscles). Procedure algorithm: At the initial stage at a certain initial position the mobile platform are determined by the generalized coordinates of axial elements of the manipulator. Then, in accordance with prescribed laws moving platform as a rigid body, are given small increments in the coordinates of its three basic points and solved the inverse kinematics problem. Thus, finding the difference between the generalized coordinates, we get their increments, corresponding to small changes in position of the moving platform in space. Optimization of the stand structures, including the determination of optimal initial configuration is based on solving the direct kinematics problem in view of minimizing the angles of pressure in the kinematic pairs and the smallest mistake to implement the required motions of the mobile platform. This concept stand allows to realize a sufficiently complex laws of motion of the moving platform with required applied loads.

Research paper thumbnail of Manipulator synthesis on the given properties of working space. Application of polynomials with linear real parameter

2010 IEEE International Conference on Systems, Man and Cybernetics, 2010

Abstract-In this work the algorithm and the results of a synthesis problem solving for three-link... more Abstract-In this work the algorithm and the results of a synthesis problem solving for three-links planar manipulator with anthropomorphous structure according to criterion of a minimum total volume of links movements is resulted at achievement by end effector of set of points in ...

Research paper thumbnail of A Novel Fatigue Testing Machine For Spinal Fixation Systems Under Various Conditions Of Loading

SAÜ Fen Bilimleri Enstitüsü Dergisi, 2012

For recent years, a new technologies of treatment of spinal disease and injuries received underwe... more For recent years, a new technologies of treatment of spinal disease and injuries received underwent rapid development. Many of them use different types of artificial implants and fixation systems. At the same time the most widely a transpedicular and ventral systems are used. If the spinal surgical operation is performed by the modern technology, patients quickly acquire the ability to lead an active life, during which the elements of the fixation systems (screws, longitudinal and transverse rods) are subjected to intensive loading and for various reasons may lose its functionality. One such reason is the fatigue of design elements.

Research paper thumbnail of Transfemoral Prosthesis with Polycentric Knee Mechanism: Design, Kinematics, Dynamics and Control Strategy

Research results obtained developing budget model of transfemoral prosthesis with polycentric kne... more Research results obtained developing budget model of transfemoral prosthesis with polycentric knee joint mechanism and microprocessor control are presented in this work. Dimensions of the mechanism links were determined on the basis of multicriteria optimization by the method of systematic investigation of parameter space with parameters uniformly distributed in multidimensional cube. Control strategy of the prosthesis with active drive units of knee and ankle joints and variable rigidity of magnetorheological damper was formulated.

Research paper thumbnail of Improving the Finite Element Simulation of Wear of Total Hip Prosthesis' Spherical Joint with the Polymeric Component

The advanced model of wear in the spherical joint of total hip prosthesis comprising an acetabula... more The advanced model of wear in the spherical joint of total hip prosthesis comprising an acetabular cup of ultra-high molecular
weight polyethylene (UHMWPE) in combination with a metal or ceramic femoral head is developed. The wear model is based on
the classical Archard-Lancaster equation in common with all other studies reported in literature. The finite element solution of the contact problem between the cup and the head was employed under the loading and angular motions conditions according to the ISO 14242-1 demands. The polymer wear in terms of cumulative linear and volume wear when the wear factor is chosen to be a function of contact pressure is first evaluated.

Research paper thumbnail of System Analysis and Synthesis of Total Hip Joint Endoprosthesis

This paper presents new design of total hip endoprosthesis, elements of whose were developed from... more This paper presents new design of total hip endoprosthesis, elements of whose were developed from the standpoint of system analysis and synthesis of biomechanical objects and devices. The main objective of this work is to increase the functional reliability of the endoprosthesis. The system approach was used in all stages of its development, including formulation of the problem and designing of manufacturing techniques.

Research paper thumbnail of A new design of a unipolar hip edoprosthesis focusing on the best quality of life of the patients during the postoperative period

Research paper thumbnail of Quantitative and qualitative estimation of the manipulator end-effector trajectory planning by synergetic criterion

In this work from several viewpoints the task of end-effector trajectory planning in two dimensio... more In this work from several viewpoints the task of end-effector trajectory planning in two dimensional workspace for the model of two link planar anthropomorphous manipulator with revolute joints is considered. The set of solutions by criteria of the minimum torques-change, the minimum total work, and also by a new criterion of the minimum error of a linear synergy are received. Their relative quantitative and qualitative estimations are made. The criterion of the minimum error of a linear synergy is proved from the biomechanical point of view. It is shown that the task of a trajectory planning at its using has solutions, which correspond to a set of experimental data and in general are characterized by kinematic and dynamic invariance, which are peculiar to free movements of the human arm. The numerical solutions of the task are received by using of the Jacobi orthogonal polynomials for various directions of end-effector movements to the target and for two variants of manipulator links parameters.

Research paper thumbnail of Modelling of a stress-strain state of transpedicular spine fixation system

For maintenance of a spine stability during the postoperative period a transpedicular fixing of i... more For maintenance of a spine stability during the postoperative period a transpedicular fixing of its elements is often used. Usually the transpedicular systems are formed of rods which as a result form a design of the frame type, fastening by screws to vertebras. Such design should be rigid and perceive loadings operating from the spine without essential deformations. From the perfection point of view of known designs their stress whole, and each of elements, in particular is of interest. In this study the modeling of the transpedicular screw is performed and estimation of its deformations taking into account interaction with a vertebra body having variable structure is made.

Research paper thumbnail of Multicriteria Synthesis of a polycentric knee prosthesis for transfemoral amputees

In one of the prosthesis designs for lower limb transfemoral amputations artificial knee joints w... more In one of the prosthesis designs for lower limb transfemoral amputations artificial knee joints with polycentric mechanisms are used. Such prostheses are characterized by high stability during the stance phase of the movement. The existing variety of polycentric mechanisms indicates the possibility of finding the optimal prosthesis design satisfying several quality criteria.In this paper we present a multicriteria method for the synthesis of the artifical polycentric knee mechanism based on the uniform systematic study of the design parameters space and on the analysis of Pareto optimal solutions.

Research paper thumbnail of New Laguerre's type method for solving of a polynomial equations systems

In this paper we present a substantiation of a new Laguerre's type iterative method for solving o... more In this paper we present a substantiation of a new Laguerre's type iterative method for solving of a nonlinear polynomial equations systems with real coefficients. The problems of its implementation, including relating to the structural choice of initial approximations, were considered. Test examples demonstrate the effectiveness of the method at the solving of many practical problems solving.

Research paper thumbnail of New Laguerre-S Type Method For Solving Of A Polynomial Equations Systems

In this paper we present a substantiation of a new Laguerre-s type iterative method for solving o... more In this paper we present a substantiation of a new Laguerre-s type iterative method for solving of a nonlinear polynomial equations systems with real coefficients. The problems of its implementation, including relating to the structural choice of initial approximations, were considered. Test examples demonstrate the effectiveness of the method at the solving of many practical problems solving.

Research paper thumbnail of Multicriteria Synthesis Of A Polycentric Knee Prosthesis For Transfemoral Amputees

In one of the prosthesis designs for lower limb transfemoral amputations artificial knee joints w... more In one of the prosthesis designs for lower limb transfemoral amputations artificial knee joints with polycentric mechanisms are used. Such prostheses are characterized by high stability during the stance phase of the movement. The existing variety of polycentric mechanisms indicates the possibility of finding the optimal prosthesis design satisfying several quality criteria.In this paper we present a multicriteria method for the synthesis of the artifical polycentric knee mechanism based on the uniform systematic study of the design parameters space and on the analysis of Pareto optimal solutions.

Research paper thumbnail of Manipulator synthesis on the given properties of working space. Application of polynomials with linear real parameter

2010 IEEE International Conference on Systems, Man and Cybernetics, 2010

Abstract-In this work the algorithm and the results of a synthesis problem solving for three-link... more Abstract-In this work the algorithm and the results of a synthesis problem solving for three-links planar manipulator with anthropomorphous structure according to criterion of a minimum total volume of links movements is resulted at achievement by end effector of set of points in ...

Research paper thumbnail of System Analysis and Synthesis of Total Hip Joint Endoprosthesis

Procedia Engineering, 2015

Research paper thumbnail of A Novel Fatigue Testing Machine For Spinal Fixation Systems Under Various Conditions Of Loading

SAÜ Fen Bilimleri Enstitüsü Dergisi, 2012

For recent years, a new technologies of treatment of spinal disease and injuries received underwe... more For recent years, a new technologies of treatment of spinal disease and injuries received underwent rapid development. Many of them use different types of artificial implants and fixation systems. At the same time the most widely a transpedicular and ventral systems are used. If the spinal surgical operation is performed by the modern technology, patients quickly acquire the ability to lead an active life, during which the elements of the fixation systems (screws, longitudinal and transverse rods) are subjected to intensive loading and for various reasons may lose its functionality. One such reason is the fatigue of design elements. Efficiency of fixation system components is determined by the quality of their surgical implantation, taking into account the mechanical characteristics of materials and the design features. It is rather difficult to take into consideration the influence of all factors and to quantify the resource of the known and newly designed structures. The most accurate estimates can be obtained through the testing only. In this work is presented a new design of the machine for fatigue tests of spinal fixation systems, which allow to obtain reliable estimates of the resource under different loading conditions.

Research paper thumbnail of Improving the Finite Element Simulation of Wear of Total Hip Prosthesis’ Spherical Joint with the Polymeric Component

Procedia Engineering, 2015

Research paper thumbnail of Evaluating the Impact and Norming the Parameters of Partially Regular Texture on the Surface of the Articulating Ball Head in a Total Hip Joint Prosthesis

Tribology Online, 2016

The theoretical study and evaluation of stress-strain condition of the friction pair's surfaces o... more The theoretical study and evaluation of stress-strain condition of the friction pair's surfaces of total hip joint prosthesis with partially regular texture on a ball head surface, depending on the values of its characteristic parameters, using finite element modeling are performed. It has allowed formulating the recommendations for dimple's spacing rationing and the extent of a surface rough site with partially regular texture, aiming to increase the prosthesis' lifespan. The problem is solved from the condition of dry or boundary lubrication. For the indicated range of nominal contact pressure in hip joint, the quantitative evaluation of allowable roughness parameters to which it is necessary to process the ball head surface for metal-on-metal and metal-on-polymer friction pairs are obtained, considering the dimple's spacing and size on the surface.

Research paper thumbnail of Modeling stress–strain state of screw transpedicular spine fixation system with variable structure of the vertebral body

Journal of Biomechanics, 2011

Research paper thumbnail of Structure and kinematics of the stand for testing implants with actuator on the basis artificial pneumatic muscle

Journal of Biomechanics, 2011

ABSTRACT Parallel manipulators, based on platform Stewart-type, have a number of advantages, whic... more ABSTRACT Parallel manipulators, based on platform Stewart-type, have a number of advantages, which are essential in the implementation of the required spatial motions of a rigid mobile platform and any fixed relative to its parts or devices. Such a problem arises, for example, if necessary, testing of implants, which replace the elements of the spine and stabilization systems of local areas of the spine, for example, transpedicular or ventral systems. During the tests necessary to most accurately reproduce the natural movement of one of the elements tested systems, and for some implants standards strictly define the test conditions. Preliminary calculations made by us have shown that the angular and linear movement of the mobile test bed, based on platform type manipulator is used by Stewart, are relatively small. In this regard, suggested as a pneumatic actuator using artificial muscles, produced by FESTO. Thus, the structure appears to stand rigid fixed platform, which is associated with the mobile platform with six artificial muscles, each of which is attached to both platforms by means of spherical joints. In a medium Solidworks we have developed three-dimensional models of stands of various types in order to assess their functional capabilities and selection of optimal, in terms of kinematics, dynamics and control. Kinematics of the Stewart platform is sufficient detail considered in many sources. Therefore the most important the task is developing an interconnected qualitative algorithm for solving direct and inverse kinematics. In future this algorithm will be used in the synthesis of system control actuators platform (artificial muscles). Procedure algorithm: At the initial stage at a certain initial position the mobile platform are determined by the generalized coordinates of axial elements of the manipulator. Then, in accordance with prescribed laws moving platform as a rigid body, are given small increments in the coordinates of its three basic points and solved the inverse kinematics problem. Thus, finding the difference between the generalized coordinates, we get their increments, corresponding to small changes in position of the moving platform in space. Optimization of the stand structures, including the determination of optimal initial configuration is based on solving the direct kinematics problem in view of minimizing the angles of pressure in the kinematic pairs and the smallest mistake to implement the required motions of the mobile platform. This concept stand allows to realize a sufficiently complex laws of motion of the moving platform with required applied loads.

Research paper thumbnail of Manipulator synthesis on the given properties of working space. Application of polynomials with linear real parameter

2010 IEEE International Conference on Systems, Man and Cybernetics, 2010

Abstract-In this work the algorithm and the results of a synthesis problem solving for three-link... more Abstract-In this work the algorithm and the results of a synthesis problem solving for three-links planar manipulator with anthropomorphous structure according to criterion of a minimum total volume of links movements is resulted at achievement by end effector of set of points in ...

Research paper thumbnail of A Novel Fatigue Testing Machine For Spinal Fixation Systems Under Various Conditions Of Loading

SAÜ Fen Bilimleri Enstitüsü Dergisi, 2012

For recent years, a new technologies of treatment of spinal disease and injuries received underwe... more For recent years, a new technologies of treatment of spinal disease and injuries received underwent rapid development. Many of them use different types of artificial implants and fixation systems. At the same time the most widely a transpedicular and ventral systems are used. If the spinal surgical operation is performed by the modern technology, patients quickly acquire the ability to lead an active life, during which the elements of the fixation systems (screws, longitudinal and transverse rods) are subjected to intensive loading and for various reasons may lose its functionality. One such reason is the fatigue of design elements.

Research paper thumbnail of Transfemoral Prosthesis with Polycentric Knee Mechanism: Design, Kinematics, Dynamics and Control Strategy

Research results obtained developing budget model of transfemoral prosthesis with polycentric kne... more Research results obtained developing budget model of transfemoral prosthesis with polycentric knee joint mechanism and microprocessor control are presented in this work. Dimensions of the mechanism links were determined on the basis of multicriteria optimization by the method of systematic investigation of parameter space with parameters uniformly distributed in multidimensional cube. Control strategy of the prosthesis with active drive units of knee and ankle joints and variable rigidity of magnetorheological damper was formulated.

Research paper thumbnail of Improving the Finite Element Simulation of Wear of Total Hip Prosthesis' Spherical Joint with the Polymeric Component

The advanced model of wear in the spherical joint of total hip prosthesis comprising an acetabula... more The advanced model of wear in the spherical joint of total hip prosthesis comprising an acetabular cup of ultra-high molecular
weight polyethylene (UHMWPE) in combination with a metal or ceramic femoral head is developed. The wear model is based on
the classical Archard-Lancaster equation in common with all other studies reported in literature. The finite element solution of the contact problem between the cup and the head was employed under the loading and angular motions conditions according to the ISO 14242-1 demands. The polymer wear in terms of cumulative linear and volume wear when the wear factor is chosen to be a function of contact pressure is first evaluated.

Research paper thumbnail of System Analysis and Synthesis of Total Hip Joint Endoprosthesis

This paper presents new design of total hip endoprosthesis, elements of whose were developed from... more This paper presents new design of total hip endoprosthesis, elements of whose were developed from the standpoint of system analysis and synthesis of biomechanical objects and devices. The main objective of this work is to increase the functional reliability of the endoprosthesis. The system approach was used in all stages of its development, including formulation of the problem and designing of manufacturing techniques.

Research paper thumbnail of A new design of a unipolar hip edoprosthesis focusing on the best quality of life of the patients during the postoperative period

Research paper thumbnail of Quantitative and qualitative estimation of the manipulator end-effector trajectory planning by synergetic criterion

In this work from several viewpoints the task of end-effector trajectory planning in two dimensio... more In this work from several viewpoints the task of end-effector trajectory planning in two dimensional workspace for the model of two link planar anthropomorphous manipulator with revolute joints is considered. The set of solutions by criteria of the minimum torques-change, the minimum total work, and also by a new criterion of the minimum error of a linear synergy are received. Their relative quantitative and qualitative estimations are made. The criterion of the minimum error of a linear synergy is proved from the biomechanical point of view. It is shown that the task of a trajectory planning at its using has solutions, which correspond to a set of experimental data and in general are characterized by kinematic and dynamic invariance, which are peculiar to free movements of the human arm. The numerical solutions of the task are received by using of the Jacobi orthogonal polynomials for various directions of end-effector movements to the target and for two variants of manipulator links parameters.

Research paper thumbnail of Modelling of a stress-strain state of transpedicular spine fixation system

For maintenance of a spine stability during the postoperative period a transpedicular fixing of i... more For maintenance of a spine stability during the postoperative period a transpedicular fixing of its elements is often used. Usually the transpedicular systems are formed of rods which as a result form a design of the frame type, fastening by screws to vertebras. Such design should be rigid and perceive loadings operating from the spine without essential deformations. From the perfection point of view of known designs their stress whole, and each of elements, in particular is of interest. In this study the modeling of the transpedicular screw is performed and estimation of its deformations taking into account interaction with a vertebra body having variable structure is made.

Research paper thumbnail of Multicriteria Synthesis of a polycentric knee prosthesis for transfemoral amputees

In one of the prosthesis designs for lower limb transfemoral amputations artificial knee joints w... more In one of the prosthesis designs for lower limb transfemoral amputations artificial knee joints with polycentric mechanisms are used. Such prostheses are characterized by high stability during the stance phase of the movement. The existing variety of polycentric mechanisms indicates the possibility of finding the optimal prosthesis design satisfying several quality criteria.In this paper we present a multicriteria method for the synthesis of the artifical polycentric knee mechanism based on the uniform systematic study of the design parameters space and on the analysis of Pareto optimal solutions.

Research paper thumbnail of New Laguerre's type method for solving of a polynomial equations systems

In this paper we present a substantiation of a new Laguerre's type iterative method for solving o... more In this paper we present a substantiation of a new Laguerre's type iterative method for solving of a nonlinear polynomial equations systems with real coefficients. The problems of its implementation, including relating to the structural choice of initial approximations, were considered. Test examples demonstrate the effectiveness of the method at the solving of many practical problems solving.